Apparatus for use with liquid enclosures



M. M. BORDEN March 1o, 1959 2,876,789

APPARATUS FOR USE WITHl LIQUID ENCLOSURES Filed Oct. 50, 1957 3Sheets-Sheet 1 Zia Z5 Zia willi/1111111115 :inventor attorneys March 10,1959 M. M. BORDEN 2,876,789

APPARATUS FUR USE WITH LIQUID ENcLosUREs Fild oct. 3o. 1957 ssheets-sheet 2- Gttornegs March 10, 1959 M. M. BORDE-N 2,376,739

I APPARATUS FOR USE WITH LIQUID ENCLOSURE'S Filed Oct. 30, 1957 3Sheets-Sheet 3 @qui l f fw. Z7 6/ 62. 48 z 63 6 0 49 Lin/ fl 'Il u f" f3I 56 I v lrv l 59a' Znvventor Mra/ZW 8g WM/aww- Gttornegs United StatesAPPARATUS FOR USE WITH LIQUID ENCLOSURES Application October 30, 1957,Serial No. 694,061 18 Claims. (Cl. 137-217) This application is acontinuation-impart of the application of Moro M. Borden, Serial No.432,265, filed May 25, 1954, now abandoned, and bearing the same titleas this application.

The invention relates to apparatus for substantially eliminating oralleviating undesired conditions that may arise in liquid enclosures,particularly in water pipe lines and the like. The invention wll bedescribed herein with reference to a water pipe line as it is primarilyfor use with such a line, but it is intended that the invenltion shallbe applicable in any instance where it may serve its purposes.

In the case of a water pipe line, a sudden decrease in pressure willcause creation of an undesirable vacuous condition. This can besubstantially prevented or alleviated by employing an air-vacuum valvein association with the pipe line. Such a valve operates, upon decreaseof the pressure in the associated pipe line to a predetermined minimumvalue, to admit air to the pipe line to relieve the low-pressure orvacuous condition and thus avoid possible collapse of the pipeparticularly if it is a thin wall pipe. The resultant rise in pressurein the pipe line causes the valve to close. Rapid closure of the valve,however, frequently causes a Water hammer action which may besuiiiciently severe to rupture the pipe even if it is a thick wall pipe.

The principal object of the present invention is to provide an apparatuswhich will overcome the above-mentioned objection.

Another object of the invention is to provide apparatus including anair-vacuum valve, wherein the rate of closure of the valve isautomatically controlled independently and irrespective of thevalve-closing pressure, so as to prevent objectionable water hammer.

Another object of the. invention is to provide in such apparatus acontroller for an air-vacuum valve employing means for controlling therate of displacement of a buiiing iiuid.

A further object of the invention is to provide in such apparatus acontroller having means whereby the rate of closing of the air-vacuumvalve may be variably controlled.

A further object of the invention is to provide in such apparatus acontroller wherein the control action is effected by means of a variablearea Venturi device.

In accordance with this invention, the closing movement of an air-vacuumvalve is impeded by a controlled damping or bufling action which governsthe rate of closure of said valve independently and irrespective of thepressure acting to close the valve. In the preferred form of theinvention, the damping or buing action is effected through controlled owof a buiiing uid in a closed circulating system which includes a ratecontroller that controls the rate of How of the bung fluid and therebycontrols the rate of closure of the air-vacuum valve. Further, in thepreferred form, the flow of the buing fluid is controlled by a ratesensing device, preferably in 'i atent the form of a Venturi device, andby a ow control means under control of the sensing device. Within thescope of the invention either the rate controller or a ow control at thesensing device may be used to achieve the specific advantages of one butnot the other. If desired, provision may be made for varying the rate ofclosure of the air-vacuum valve according to the instantaneous positionof the valve. This is achieved, in the preferred embodiment, byproviding an adjustable Venturi device and means for adjusting the sameaccording to the instantaneous position of the air-vacuum valve duringits closing movement.

The invention may be fully understood from the following detaileddescription with reference to the preferred embodiment illustrated inthe accompanying drawings.

In the drawings,

Fig. 1 is a sectional elevational view illustrating a dual arrangementconnected to a water pipe line or conduit and located in a pit above thepipe line, such dual arrangement comprising two air-vacuum valves andassociated controllers;

Fig. 2 is a vertical section through one of the airvacuum valves and theassociated super-structure forming part of the controller;

Fig. 3 is a larger scale vertical section through the dow-controllingportion of the controller;

Fig. 4 is a detail sectional view on the line 4-4 of Figure 3;

Fig. 5 is a vertical cross section on the line 5-5 of Fig. 3;

Fig. 6 is a sectional view on the line 6 6 of Fig. 3;

Figs. 7 to 12 inclusive are side views of various cam plates that may beemployed in the controller; and

Fig. 13 is a fragmentary vertical section showing a modified form of theVenturi device.

Referring first to Fig. 1, there is shown in cross-section a portion ofa water pipe line or conduit P to which two air-Vacuum valves R areconnected, each being controlled according to the preferred form of thepresent invention. The dual arrangement shown is merely for the purposeof illustration, the main purpose being to shown different arrangementsfor air intake as hereinafter described. In practice, a singleair-vacuum valve may be used, although of course more than one valve maybe used if conditions require it.

The dual arrangement shown comprises a cross-fitting F connected to thetop outlet of the pipe line, pipe elbows E, gate valves G betweenfitting F and elbows E, air-vacuum valves R and controllers C associatedwith the valves R. This assembly is located in a pit A located above thepipe line P.

Each air-vacuum valve R and the associated controller C is a completeoperative combination. Fig. 2 shows one of the air-vacuum valves (theright hand one in Fig. 1) and the associated super-structure which formspart of the controller. Fig. 3 shows the buflng fluid controlling systemwhich forms the other part of the same controller.

Referring to Fig. 2, the air-vacuum valve R and the associatedsuper-structure comprise a vertically movable valve member 12 that seatsupwardly in a valve seat 13 carried by the valve housing 14, a piston 15located in an upper housing 16, a rod 17 extending upwardly from valvemember 12 to thrust against the piston 15, a flexible diaphragm 18secured to the piston 15 and piston housing 16, and spring-loadedupwardly-seating check valves 19 carried by a transverse wall 20 whichdivides the upper housing into a lower buiiing fluid-delivery chamber 21and an upper buliing uid-rcceiving chamber 22, which communicate withthe buliing uid Aflow controlling system presently to be described. Thetransverse wall also slidably retains the central stem 15a connected topiston 15 to guide the vertical movement of the piston. 1t will be seenthat the piston 15 forms the bottom of the lower chamber 21, and thediaphragm 18 closes the space between the piston and the adjacent wallwhile permitting movement of the piston. The buiing uid is shown in Fig.2 but is omitted in Fig. 3 for the sake of clarity of illustration.

The diaphragm 18 is formed from a tube or sleeve of flexible material,such as rubber, which is` bent or folded as shown. One part of thediaphragm sleeve is secured to the piston housing and is stationary,while the other part after folding is attached to the movable piston.With this type of diaphragm the eiective area remains constantthroughout the operating stroke of the piston, and furthermore themovement ofthe piston is substantially unimpeded.

The movable valve member 12 is partially counterbalanced by thecounterweight 23 on pivoted arm 23a which has a bifurcated end engaginga collar lixed on rodV 17. The rod is slidably supported by lower andupper plates24 and 25 ot' intermediate section 25a, and a sealing ring26 carried by the plate 24 surrounds the rod. The upper end of the rodthrusts against the piston 15 by means of a thrust button 27.

An open bottomed oat 2S extends downwardly from the valve member 12 andis guided by a center rod 29 and a spider 30. The valve housing 14 isprovided with acylindrical wall 31 in spaced surrounding relation to thefloat 28, forming a oat chamber having an inlet 32 which communicateswith the pipe line P (Fig. l) through elbow E, gate valve G and fittingF,

Under normal ow conditions in the pipe line P, water is present in theoat chamber 31 and air trapped within the float is compressed somewhatgiving buoyancy to the oat, and the valve R is closed and is held closedwhile normal pressure conditions exist in the pipe line. Thecounterweight 23 is arranged so that a small depth of water around theopen-ended float 28 will keep the valve closed, but in the absence ofsuch water the valve will open by virtue of the weight of the movableassembly comprising member 12, rod 17 and oat 2?. When and if the waterlevel falls and a low pressure or vacuous condition is created, thevalve R opens and air enters through the valve past the tioat 28 andinto the pipe line. This air enters the interior of the valve housing 14by means of an opening 33 having a pipe connection 34 which may lead toa point outside the pit as yindicated at the right-hand unit of Figure lor a pipe connection 35 directed within the pit as indicated at theleft-hand unit of vEigure l.y increase of pressure causes closure of thevalve but the rate ot' valve closure is controlled by the controller nowto be further described. Prior to complete closure of the valve, air andwater Amay ow out through thevalve.

Referring now to Figures 3 to 6 and particularly Fig, 3, therate-controlling portion of the controller C comprises in general ahousing 46, a valve 41 actuated by a springbiased pressure diaphragm 42,a Venturi device including an adjustable. plug 43, an inter-connection44 between the annular chamber 45 and the chamber 46 below the diaphragm42, a control cam 47 for adjusting plug 43, and actuator means 48 forthe cam 47.

The actuator means 48 is connected by a link 49 to a lever 50`pivoted at51 (see Fig. 2) in the intermediate section 25a and having forkedconnection at 52 with a collar 53 carried by the rod 17 of the valvemember 12.

The Venturi device, ofwhich plug 43 is a part, establishes differentialpressure on the diaphragm 42 according to the rate of flow of thebufling fluid, and the diaphragm controls the positionof valvefil tomaintain arsubstantially constant rate of-tlow of thebufing fluid.Variation of the rateot owis effected, during closing movementoffvalvemember 12, byrmeans of the cam 47 which may take any of variousforms as shown in Figs. 7 to l2 and hereinafter described.

Considering the operation of the controller as a whole, and assumingthat the closing movement of valve member 12 is taking place, the piston15 (Fig. 2) is moved upwardly and acts as a pump to force the buliinguid under pressure from the lower buing liquid chamber 21 through port54 into the chamberSS (Fig. 3) of the diaphragm-actuated valve 41 whichhas V ports. The valves 1S (Fig. 2) in the wall 20 are closed duringthis upward movement of the piston. The buing lluid ows through thevalve 41 into the chamber 56 above the diaphragm 42, into the entrance45a of the Venturi device, through the latter and through port 56a intothe upper receiving chamber 22. At the same time, the pressure at thedownstream end of the Venturi device is communicated to the lower sideof diaphragm 42 through ports 57, annular space 45 and conduitconnection 44. The diaphragm 42 is biased upwardly by spring 5S whichtends to maintain maximum opening of the throttle valve 4l. Thedilerential pressure on the diaphragm causes the latter to adjust thevalve 41 to whatever setting is necessary to maintain or establish therate of tio-w of the bufling tiuid according to the adjustment of plug43. When the valve R again opens, the piston 15 moves downward and theweight of the buiiing lluid in chamber 22 causes the valves 19 to open,whereupon the buiiing duid iiows into the delivery chamber 21 and theapparatus is ready for repeat operation.

it will be seen from the foregoing that the controller functions tocontrol the rate of flow of the buing uid and thus controls the rate ofclosing of the valve member 12 independently and irrespective of theclosing pressure exerted on the valve member 12 by the pressure in thepipe line P. Stated in another way, the controller constitutes a meansof controlling the rate of closure of the valve member 12, independentlyof the closing pressure exerted on the valve member, by controlling therate of displacement or transmission of the buiiing fluid through thecontroller.

Reverting now to the actuating means 48 for the rate control cam 47, andreferring particularly to Figs. 3 and 6, it will be seen that theactuating means comprises a lever 59 forked atei) for pivotal connectionby means of pin 61 to the ears 62 of the housing 40. The actuatingmechanism further comprises a second lever 63 independently fulcrumed onpin 61 and engageable by adjustable screws 59a and 5% carried by lever59, and a cam rod 54 mounted for vertical movement in a bracket 65secured to the housing 4() and having pin and slot connection at 66 withthe lever 63. The cam 47 is secured to 'the cam rod 64 by clamp screws67, there being slots 68 in the cam to enable adjustment. The camsurface of the cam engages the knob 69 secured to the stem 70 of plug473. The knob is maintained in engagement with the cam by a spring '71.

ln Figure 3, the actuating means is shown in a mid position in which theVenturi device is at maximum setting. As the cam 47 moves downward underthe inliuence of the closing movement of the air-vacuum valve member 12,the inclined cam surface '72 of cam 47 causes movement of plug 43 towardthe left to effect gentle seating of the valve member 12. The particularconfiguration of the cam 47 illustrated in Figure 3 is such that duringthe rst portion of the closing movement of the valve member 12, the atdwell 73 of the cam allows the Venturi device 43 to remain fully open,and during the remaining portion of the closing movement of the valvemember 12 the Venturi device is actuated by the inclined surface 72 ofthe cam. As cam 47 pushes plug 43 into its Venturi passage, the throatarea is reduced, the throatvelocity momentarily increased and thepressure at the throatlowered, which condition will cause the throttlingof valve 41 by the reduction of its V port area until adierentialpressure which balances the spring action of the spring 58 ispresent. Thus a similar velocity is present in the reduced Venturi areaat the equilibrium of the diaphragm load and the spring reaction.Successive reductions of throat area and buliing liquid govern the rateof closure of valve member 12 by diminishing the volume of buflingliquid which is permitted to flow through the Venturi section.

Thus, the valve member 12 closes rapidly for a portion of its stroke andthen slows down by reason of the throttling action caused by the cam.Adjustment for the throttling portion of the cam stroke is provided bymeans of the adjusting screw 59a carried by the lever 59, and adjustmentfor the return portion of the cam stroke is provided by means of theadjusting screw 59b.

By employing cams of different forms, such as cams 47a to 47f in Figs. 7to 12 inclusive, various closing actions of the valve member 12 may beobtained. For example, by employing either of the cams 47a and 47b shownin Figs. 7 and 8, a single setting of the Venturi device may beobtained, with the rate of closure of the valve member 12 depending onsuch setting. Stated in another way, the Venturi device would be set toa fixed venturi area which would re-main constant throughout the closingstroke of the valve member 12. The cam 47c illustrated in Fig. 9 wouldresult in a gradual but uniform reduction of Venturi area, and the cam47d of Fig. would result in a greater uniform reduction in Venturi area.The cam 47e of Fig. 11 is similar to that of Fig. 3 but would hold theno reduction area for a longer period and would cause reduction of areamore rapidly. The cam 47f of Fig. 12 would cause initial reduction ofthe Venturi area, then increase of the area, and finally decrease of thearea.

Fig. 13 shows a modified form of the Venturi device where the downstreampressure is derived at a location beyond the end of plug 43. It shouldbe noted that the ports through which the downstream pressure is derivedmay be disposed at the most advantageous angle. This applies to both ofthe embodiments shown in Figs. 3

' and 13.

It will be obvious to those skilled in the art that either a controlinvolving the rate sensing device or a rate con` troller including therate sensing device only may be used each to achieve limited advantagesnot available in the prior art. Since only omission of parts isrequired, neither modification need be shown and either may be readilyunderstood from the drawings in the present case. Thus, a control usingthe rate sensing device would omit the valve 41, or at least not make itadjustable in accordance with pressure changes, as well as omitting itsadjusting structure including diaphragm 42. Moreover, chambers 4S and 46and their interconnection 44 would be unnecessary. The results of theseomissions would be to have the plug 43 repositioned in accordance withthe pattern of cam 47 depending upon the position of the valve. Theeffect would be to provide different amounts of restriction to the flowof the bufllng fluid in different positions of the valve.

On the other hand, the cam 47, cam follower knob 69, the spring 71, andthe moving parts having to do with the repositioning of plug 43 inresponse of the position of the valve might be omitted, and the plug 43fixed in position or made manually adjustable. The effect of thisarrangement would be to establish a predetermined rate of flow by thesensing means and to keep that rate of flow constant.

In the use of the apparatus provided by this invention, any suitablebutllng fluid may be used. Such fluid should have no corrosive effect onmetals and no destructive effect on rubber; it should be non-freezing;and its viscosity should be substantially unaffected by temperaturechanges. Liquids having these properties commonly used in liquidpressure systems may be used When the apparatus is first put intooperation, the buffing fluid is poured in through the chamber 22 (Fig.2), afterremoving the cover, until the fluid occupies all of thecontroller except the greater part of the upper chamber 22 which`receives the displaced fluid during operation as above described.

For proper operation of the apparatus, it is important that thecounterbalancing of the valve member 12 and the associated elements issuch that there is enough unbalanced weight to effect quick opening ofthe valve but not enough unbalanced weight to adversely affect theclosing of the valve. It should be noted that in the arrangement shown,the link 49 and lever 59 effect some counterbalance, and the weight 23provides the rest of the required counterbalance.

From the foregoing description, it will be seen that the inventionprovides apparatus wherein an air-vacuum valve is quick opening toquickly relieve any low pressure or vacuous condition that may developin the associated pipe line or liquid enclosure, and wherein the closingof the valve is controllably impeded by the bufling means associatedwith said valve. The controlled closure of the valve alleviates Vorsubstantially eliminates water hammer. Y

While a preferred embodiment of the invention and certain modificationshave been illustrated and described, the invention is not limitedthereto 4but contemplates such further modifications and embodiments asmay occur to those skilled in the art.

What is claimed is:

1. In an apparatus for use with a liquid conduit, an air-vacuum valveadapted to be connected to such conduit and having a valve membermovable upwardly by pressure in said conduit to valveclosing positionand free to move downwardly by gravity upon decrease of pressure in saidconduit, a first stationary bufling fluid chamber above said valve andhaving a piston movable upwardly by said member, a second stationarybung fluid chamber above said first chamber, valve means between saidchambers permitting downward movement of buffing fluid from the secondto the first chamber but preventing upward movement of the buffingfluid, means providing a flow path for the bufling fluid from the firstchamber to the second chamber, the upward movement of said pistoncausing flow of bulllng fluid through said flow path, means in said flowpath for continuously sensing the rate of flow, and means responsive tosaid sens ing means for controlling the flow of the bufling fluid toobtain predetermined demanded rates of flow thereby to control the rateof closure of said air-vacuum valve.

2. In an apparatus for use with a liquid conduit, an air-vacuum valveadapted to be connected to such conduit and having a valve membermovable upwardly by valve-closing position and means between saidchambers permitting downward movement of bufling fluid from the secondto the first chamber but preventing upward movement of the butlingfluid, means providing 'a flow path for the but`u`ng fluid from thefirst chamber to the second chamber, the upward movement of said pistoncausing flow of buflng fluid through said flow path, means in said flowpath for continuously sensing the rate of flow, and means responsive tosaid sensing means for controlling the flow of the bufflng fluid toobtain predetermined demanded rates of flow thereby to control the rateof closure of said airvacuum valve.

3. In an apparatus for use with a liquid conduit, an air-vacuum valveadapted to be connected to such conduit and having a valve membermovable upwardly by 4 pressure in said conduit to valve-closing positionandI free to. move downwardly bygravity upon decrease of. pressure in.said conduit,` alirst stationary buing uid chamber above said valveandhaving a piston movable upwardly by said member, a second stationarybuing iluid chamber above said lirst chamber, valve means bctween saidchambers permitting downward movement of.

bufling fluid from the second to the first chamber but preventing upwardmovement of the bufling duid, means providing a flow path for the butinguid from the first chamber to the second of said piston causing flow ofbufng iluid through said flow path, means for controlling the flow ofthe buing fluid thereby to control the rate of closure of said airvacuumvalve, means in said tlow path for continuously sensing the rate of ow,and means responsive to said sensingmeans for varying the rate of ilowof the buiing tluid to obtain predetermined demanded rates of ow andconsequently Vthe rate of closure of said air-vacuum valve according tothe instantaneous position of said valve.

4. In an apparatus for use with 'a liquid conduit, an air-vacuum valveadapted to be connected to such conduit and having a valve membermovable upwardly by pressure in said conduit to valve-closing positionand free to move downwardly by gravity upon decrease ot pressure in saidconduit, a rst stationary bufling duid chamber above said valve andhaving a piston movable upwardly by said member, a second stationaryhurling fluid chamber above said irst chamber, valve means between saidchambers permitting downward movement of bufng uid from the second tothe tirst chamber but preventing upward movement of the bufng fluid,means providing a ow path for the buhng fluid from the lirst chamber tothe second chamber, the upward movement of said piston causing ow ofhurling `liuid through said flow path, a Venturi device to sense rate ofow of the bufling fluid, and means under control of said device forgoverning the rate of ilow of the builing lluid thereby to control therate of closure of said air-vacuum valve.

5. In an apparatus for use with a liquid conduit, an air-vacuum valveadapted to be connected to such conduit and having a valve membermovable upwardly by pressure in said conduit to valve-closing positionand free to move downwardly by gravity upon decrease of pressure in saidconduit, a lirst stationary buing uid chamber above said valve andhaving a piston movable upwardly by said member, a constant-areadiaphragm closing the space about said piston and allowing unrestrainedmovement-of the piston, a second stationary bufting luid chamber abovesaid Vtirst chamber, valve means between said chambers permittingdownward movement of hurling-fluid from the second to the first chamberbut preventing upward movement of the buing uid, means providing a dowpath for the boiling lluid from the first chamber to the second chamber,the upward movement of said piston causing flow of butting uid throughsaid ilow path, a Venturi device to sense rate of ow of the buliing uid,and means under control or" said device for governing the rate of flowof the buing duid thereby to control the rate of closure of saidair-vacuum valve.

6. ln an apparatus for use with a liquid conduit, an air-vacuum valveadapted to be connected to said conduit and having a valve membermovable upwardly by pressure in said conduit to valve-closing position,a first stationary bufng uidv chamber above said valve and having apiston movable upwardly by said member, a second stationary builingiluid chamber above said rst chamber, valve means between said chamberspermitting downward movement of buliing lluid from the second to thelirst chamber but preventing upward movement of the bulling liuid, meansproviding a llow path for the bufing uid from the first chamber tothesecond charnber, the upward movement of said piston causing llow ofbufling iiuid through said llow path, an adjustable Ven turi device tosense rate-of dow ot the bufling fluid, lmeans chamber, the upwardmovement for adjusting said device,

valvemember to move said cam means, thereby to et`' feet control of therate of tlow of the butting uid acment of said air-vacuum valve toetlect flow of the under-control orsaiddevice foigoverning the rate ofow of the bufng uid so as lto control the rate of closure of saidair-vacuum valve,- and means `for varying rthe adjustment of said deviceand liow of the buing fluid according to the instantaneous position ofYsaid valve.

7. ln an apparatus for use with a liquid conduit, an air-vacuum valveadapted to be connected to said conduit and having a valve membermovable upwardly by pressure in said conduit to valve-closing position,a first stationary bufling duid chamber above said valve and having apiston movable upwardly by said member, a second stationary butiingiluid .chamber above said first chamber, valve means between saidchambers permitting downward movement of buing iuid from the vsecond tothe lirst chamber but preventing upward movement of the buliing liuid,means providing a flow path for the bulling lluid from the first chamberto the second chamber, the upward movement of said piston causing ow ofbuiiing iluid through said ow path, an adjustable Venturi device tosense rate of flow of the buffing fluid, means under control of saiddevice for governing the rate of dow of the bufng fluid so as to controlthe rate of closure of said air-vacuum valve, movable cam means andmeans operable by said cording to the instantaneous position of saidvalve member.

8. In an apparatus for use with a liquid enclosure, an air-vacuum valveadapted to be connected to such enclosure for the alleviation ofundesirable pressure conditions therein, said air-vacuum valve beingfree to open upon decrease of pressure in said enclosure and beingclosed by pressure in said enclosure, a stationary bulng iluid cylinder,means providing a llow path for buffing fluid externally of saidcylinder from one portion to another portion thereof, means operable byclosing movement of said air-vacuum valve to elect llow of the buftingiluid in said llow path, means in said ow path continuously sensing therate of ow, means responsive to said sensing means for controlling therate of flow of the buliing fluid to obtain predetermined demanded ratesof flow so as to control the speed of closing of said airvacuum valve.

9. In an apparatus for use with a liquid enclosure, an air-vacuum valveadapted to be connected to such enclosure for the alleviation ot'undesirable pressure conditions therein, said air-vacuum valve beingfree to open upon decrease of pressure in said enclosure andlbeingclosed by pressure in said enclosure, a stationary buing fluid cylinder,means providing a ow path for bufling fluid externally of said cylinderfrom one portion to another portion thereof, means operable by closingmovebuing lluid in said ilow path, means in said ow path continuouslysensing the rate of liow, means responsive to said sensing means forcontrolling the rate of ilow of the bufling fluid to obtainpredetermined demanded rates of how so as to control the speed ofclosing of said airvacuum valve, and means for varying the predeterminedrates of llow of the buiiing fluid and consequently the rate of closureof said air-vacuum valve according to the instantaneous position of thevalve.

l0. In an apparatus for use with a liquid enclosure, an air-vacuum valveadapted to be connected to such enclosure for the alleviation otundesirable pressure conditions therein, said air-vacuum valve beingfree to open upon decrease of pressure in said enclosure and beingclosed by pressure in said enclosure, a pair of intercommunicatingstationary buing duid chambers, valve means between said chambers tolimit ow of bufling iluid di'- rectly therebetween to one direction,means providing a ilow path for the buling fluid between said chambers,

means operable by closing movement of said air-vacuum.

consequently the rate ofv valve to eect flow of the bufng iluid in saidflow path, means in said ow path continuously sensing the rate of flow,and means responsive to said sensing means for controlling the rate ofow of the butiing uid to obtain predetermined demanded rates of ow so asto control the speed of closing of said air-vacuum valve.

1l. In an apparatus for use with a liquid enclosure, an air-vacuum valveadapted to be connected to such euclosure for the alleviation ofundesirable pressure conditions therein, said air-vacuum valve beingfree to open upon decrease of pressure in said enclosure and beingclosed by pressure in said enclosure, a pair of intercommunicatingstationary butiing fluid chambers, valve means between said chambers tolimit flow of buing uid directly therebetween to one direction, meansproviding a flow path for the butng uid between said chambers, meansoperable by closing movement of said air-vacuum valve to effect ow ofthe butng uid in said ow path, means in said ow path continuouslysensing the rate of ow, means responsive to said sensing means forcontrolling the rate of ow of the buing fluid to obtain predetermineddemanded rates of ow so as to control the speed of closing of saidair-vacuum valve, and means for varying the predetermined rates of tlowof the bung uid and consequently the rate of closure of said airvacuumvalve according to the instantaneous position of the valve.

12. In an apparatus for use with a liquid enclosure, an air-vacuum valveadapted to be connected to such enclosure for the alleviation ofundesirable pressure conditions therein, said air-vacuum valve beingfree to open upon decrease of pressure in said enclosure and beingclosed by pressure in said enclosure, a stationary buing huid cylinder,means providing a ow path for buing fluid externally of said cylinderfrom one portion to another portion thereof, means operable by closingmovement of said air-vacuum valve to eect iow of the butng liuid in saidow path, a Venturi device in said flow path for sensing the rate of owof the butiing fluid therein, and means under control of said device forgoverning the rate of flow of the buling uid thereby to control the rateof closure of said air-vacuum valve.

13. In an apparatus for use with a liquid enclosure, an air-vacuum valveadapted to be connected to such enclosure for the alleviation ofundesirable pressure conditions therein, said air-vacuum valve beingfree to open upon decrease of pressure in said enclosure and beingclosed by pressure in said enclosure, a stationary buing fluid cylinder,means providing a ow path for buting lluid externally of said cylinderfrom one portion to another portion thereof, means operable by closingmovement of said air-vacuum valve to eiect ow of the bung iluid in saidow path, an adjustable Venturi device in said ow path for sensing therate of ilow of the bulmg tuid therein, means under control of saiddevice for governing the rate of flow of the buh'ing Huid thereby tocontrol the rate of closure of said air-vacuum valve, and means forvarying the adjustment of said device and consequently the rate of ow ofthe buihng uid according to the instantaneous position of saidair-vacuum valve.

14. In an apparatus for use with a liquid enclosure, an air-vacuum valveadapted to be connected to such enclosure for the alleviation ofundesirable pressure conditions therein, said air-vacuum valve beingfree to open upon decrease of pressure in said enclosure and beingclosed by pressure in said enclosure, a pair of intercommunicatingstationary buthng uid chambers, valve means between said chambers tolimit How of buing Huid directly therebetween to one direction, meansproviding a liow path for the buing tluid between said chambers, meansoperable by closing movement of said air-vacuum valve to effect ow ofthe buthng uid in said ow path, a Venturi device in said tlow path forsensing the rate of flow of the buiing fluid therein, and means undercontrol of said device for governing the rate of ow of the buing uidthereby to control the rate of closure of said airvacuum valve.

15. In an apparatus for use with a liquid enclosure, an air-vacuum valveadapted to be connected to such enclosure for the alleviation ofundesirable pressure conditions therein, said air-vacuum valve beingfree to open upon decrease of pressure in said enclosure and beingclosed by pressure in said enclosure, a pair of intercommunicatingstationary buing tluid chambers, valve means between said chambers tolimit ow of bufng lluid directly therebetween to one direction, meansproviding a flow path for the buiiing uid between said chambers, meansoperable by closing movement of said air-vacuum Valve to elect flow ofthe buing uid in said tio-w path, an adjustable Venturi device in saidow path for sensing the rate of ow of the buing uid therein, means undercontrol of said device for governing the rate of tlow of the buiiing uidthereby to control the rate of closure of said air-vacuum valve, andmeans for varying the adjustment of said device and consequently therate of tiow of the buing fluid according to the instantaneous positionof said air-vacuum valve.

16. In an apparatus for use with a liquid conduit, an air-vacuum valveadapted to be connected to such conduit and having a valve membermovable upwardly by pressure in said conduit to valve-closing positionand free to move downwardly by gravity upon decrease of pressure in saidconduit, a lirst stationary buing iluid chamber above said valve andhaving a piston movable upwardly by said member, a second stationarybutlng iiuid chamber above said first chamber, a valve means betweensaid chambers permitting downward movement of buing tluid from thesecond to the first chamber but preventing upward movement of the buingfluid, means providing a flow path for the butiing fluid from the firstchamber to the second chamber, the upward movement of said pistoncausing How of bufling uid through said ilow path, means in said ow pathfor controlling the flow of the buing tluid thereby to control the rateof closure of said air-vacuum valve, said means including an adjustablemember for adjusting the rate of ow, and a coupling to a portion of themovable part of the valve whereby in the successive positions of thevalve the adjustable member is located in a predetermined position.

17. The apparatus of claim 16 in which the adjustable portion of therate controlling means is spring biased against a cam member whichdetermines the rate of ow which it permits and the position of the cammember is adjusted in response to the position of the valve.

18. The apparatus of claim 17 in which the cam member is interchangeablewith other cams to provide a selection of patterns of rate of valveclosure.

References Cited in the file of this patent UNITED STATES PATENTS937,484 Sturgess Oct. 19, 1909 2,135,383 Borden Nov. 1, 1938 2,369,510White Feb. 13, 1945 2,580,433 Kam Jan. 1, 1952 FOREIGN PATENTS 174,361Germany July 24, 1906

